At present, a hot topic that the organizations for standardization discuss is the interworking between an evolved Third Generation Partnership Project (3GPP) network and a non-3GPP network. The evolved 3GPP network includes two projects: long term evolution (LTE) and system architecture evolution (SAE). The LTE focuses on improving air interfaces, and the SAE focuses on improving the core network. For example, two interfaces (S101 and Sx-U) are added between a 3GPP network and a high rate packet data (HRPD) network for interconnecting the two networks. The S101 interface connects a mobility management entity (MME) and an enhanced access network (eAN). Essentially, the S101 interface is a tunnel and is used to forward signaling messages between a mobile station (MS) and a target network so as to assist the MS in pre-registration on the target network or handover from the source network to the target network. The Sx-U interface connects a serving gateway and an HRPD serving gateway (HSGW), and is used to forward the remaining user data in the evolved 3GPP network to the HRPD network. Then the HRPD network sends the data to the MS.
Assume that a dual-mode MS has only one transmitter, that is, the MS can send data on only one type of networks. In this case, when sending and receiving data on a network, the MS cannot perform registration, authentication, or session negotiation on another network. As a result, before performing handover between different access technologies, the MS must spend one to two seconds on registration, authentication, or session negotiation. This interrupts data transmission, thus greatly affecting the quality of real-time services during handover. To reduce the interruption time of real-time services during handover, the pre-registration is put forward. That is, an MS performs registration, authentication, or session negotiation on the target network through the tunnel from the source network to the target network while sending and receiving data on the source network. When performing inter-network handover, the MS can send and receive data on the target network immediately. This greatly reduces the service interruption time during inter-network handover.
After the MS performs pre-registration and before the MS is handed over to the target network, the MS can perform signaling interaction with the target network through the source network and the tunnel between the source network and the target network (for example, the S101 interface between the 3GPP network and the HRPD network) at any time, if required. For example, when the configuration information of the quality of service (QoS) changes, the MS re-negotiates session information with the target network.
To ensure that the MS can perform signaling interaction with the target network through the tunnel between the source network and the target network after the MS performs pre-registration and before the MS is handed over to the target network, the interconnected network needs to support the tunnel switching between the source network and the target network.
For example, after the MS performs re-registration and before the MS is handed over to the target network, the MME or the AN may be changed due to mobility management. The following takes the interconnection between an evolved 3GPP network and an HRPD network as an example. Specifically, four scenarios are provided, as shown in Table 1.
TABLE 1Session Context transfer of the MSinformation transfer of [from the source MME to the MS [from the source the target MME]AN to the target AN]The MS is currentlyThe MS moves to the The MS moves within served by the target MME from the the management scope of evolved 3GPP current MME. The MS, the current MME. The network.however, does not leave MS, however, leaves the the management scope ofmanagement scope of the the AN associated with AN associated with the the source MME. The source MME and enters source MME enables the management scope of MME relocation to the target AN. The MS transfer the contexts of the registers with the target MS to the target MME. AN through the new (scenario 1)S101 interface to transfer the session information of the MS to the target AN from the source AN. (scenario 2)The MS is currentlyThe MS moves within the The MS leaves the served by themanagement scope of the management scope of the HRPD network.current AN. The MS, current AN and enters the however, leaves the management scope of the management scope of the target AN. The MS, MME associated with the however, does not leave current AN and enters the the management scope of management scope of the the MME associated with target MME. The MS the source AN. The registers with the target source AN enables AN MME through the new session transfer to S101 interface to transfer transfer the sessions of the contexts of the MS to the MS to the target AN. the target MME from the (scenario 3)source MME.(scenario 4)
In scenario 1, the source MME enables MME relocation to transfer the contexts of the MS to the target MME. The target MME sets up a new S101 tunnel for the MS, but the AN does not know whether the new S101 tunnel is set up for an MS without session information or is used to replace a current existing S101 tunnel. When the AN needs to send a signaling message to the MS, the AN still sends the signaling message to the source MME through the original S101 tunnel for forwarding. Therefore, the MS is disconnected from the source MME and thus the signaling message from the AN cannot be sent to the MS.
In scenario 3, the source AN enables an AN session transfer to transfer the sessions of the MS to the target AN. The target AN sets up a new S101 tunnel for the MS, but the MME does not know whether the new S101 tunnel is set up for an MS without session information or is used to replace a current existed S101 tunnel. When the MME needs to send a signaling message to the MS, the MME still sends the signaling message to the source AN through the original S101 tunnel for forwarding. Obviously, the MS is disconnected from the source AN and thus the signaling message from the MME cannot be sent to the MS.
Thus, in the implementation of the prior art, the S101 tunnel cannot be switched in scenarios 1 and 3, which may make messages lost.